1. Field of the Invention
This invention relates to a method for the production of a composite material exhibiting excellent qualities such as high strength, light weight, insulating property, and good toughness and to a composite material produced by this method.
2. Description of the Prior Art
Various methods have been heretofore proposed and adopted for the production of composite materials having reinforcing fibers bound with a matric material such as, for example, a thermoplastic synthetic resin. The present inventors also earlier proposed a method disclosed in JP-B-51(1976)-33148 and JP-A-4(1992)-303626 which comprises mixing reinforcing fibers with a powdery or granular thermoplastic resin and thermally forming the resultant mixture. Since such conventional methods invariably adopt a procedure which comprises mixing a powdery or granular thermoplastic resin as a matrix material with reinforcing fibers and thermally forming the resultant mixture in a desired shape, they encounter difficulty in obtaining a product having the reinforcing fibers uniformly dispersed in the matric material. This is because the two components are not easily to mix uniformly and, after mixing, the powdery or granular resin tends to separate from the mixture. To ensure completely uniform mixture of the reinforcing fibers and the matric resin, it is necessary that the freshly produced mixture be immediately subjected to thermal formation. The product of this thermal formation is therefore limited to the simple shape of flat sheet. As disclosed in JP-B-6(1994)-71768 and U.S. application Ser. Nos. 08/035,204 and 08/335,971, the present inventors developed a fiber separating and throwing apparatus which is capable of forming a composite mat having the component fibers of matric resin fiber bundles and reinforcing fiber bundles uniformly mixed with good separation and distribution and succeeded in using the apparatus to produce a fiber-reinforced composite material which exhibits perfect shape-retaining property and high resistance to separation of the reinforcing fibers and the matrix resin, and allows easy handling of the mixture mentioned above.
Since fiber-reinforced composite material taught by JP-B-6(1994)-71768 uses a thermoplastic resin alone as a matric material, however, it is unsufficient in resistance to heat and consequently not suitable for practical applications.